Absolutely nothing. Don't even use the sims limb dampners anymore. But I do shoot a heavy arrow and don't give a hoot about
How fast it runs thru the chrono.
If tied on correctly and cut to the right length, nothing beats cat whiskers. They are also more durable than some other types of silencers like string leaches. As noted above, string stops (which most bows come with now) might render string silencers unnecessary, but you will not know for sure until you have tried it with and without them on your specific rig.